1. Field of the Invention
The present invention relates to a fuel injection apparatus for internal combustion engines, and more particularly to a fuel injection apparatus in which maximum fuel injection can be adjusted in accordance with the fuel injection advance.
2. Description of the Prior Art
The control of the amount of fuel injection, especially the control of the maximum amount of fuel injection, of the conventional fuel injection apparatus for internal combustion engines is generally determined on the basis of the rotational speed of the internal combustion engine. However, in Japanese Utility Model Public Disclosure No. 136138/81, there is proposed an apparatus in which the maximum amount of fuel injection is controlled depending upon whether or not the apparatus is in the state that free-acceleration is possible. On the other hand, in controlling the timing of fuel injection, not only the rotational speed of the engine, but also the acceleration of the engine, the coolant temperature, the engine load and the like are generally taken into consideration (e.g., Japanese Patent Publication No. 39285/76).
The control of fuel injection timing in the conventional fuel injection apparatus has a large effect on the smoke limit characteristic of the internal combustion engine, in other words, on the limit characteristic defined by a predetermined limit value for the amount of smoke produced. That is, when the timing of fuel injection varies within a predetermined adjustment range, even if the engine speed and the amount of fuel injection are not changed, the amount of smoke in the exhaust gas varies. Therefore, a fuel injection apparatus constituted by a combination of the prior art apparatuses described above has a disadvantage in that, even when the engine speed is maintained constant, an amount of smoke exceeding a predetermined value is sometimes produced depending upon the fuel injection timing. This is especially true under engine operation under the maximum amount of fuel injection.
One way for overcoming this disadvantage is to set the maximum fuel injection at a relatively low level over the required speed range in order to suppress the amount of smoke to a desired limit level under any condition of fuel injection timing adjustment whatever. However, in the case that the maximum fuel injection is set in this manner, there arises the disadvantage that the power of the engine is sometimes sacrificed.